In order to support higher data rate and spectrum efficiency, the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) system has been introduced into 3GPP Release 8 (R8) (LTE Release 8 may be referred to herein as LTE R8 or R8-LTE). In LTE, in order to schedule the downlink (DL) transmission, the eNodeB relies on Channel Quality Indicator (CQI) reports transmitted by the User Equipment (UE) in the uplink (UL). Two modes of CQI reporting may be supported in LTE, aperiodic and periodic.
LTE Advanced (which includes LTE Release 10 (R10) and may include future releases such as Release 11, also referred to herein as LTE-A, LTE R10, or R10-LTE) is a further evolution of the LTE standard that provides a 4G upgrade path for LTE and 3G networks. In LTE-A, carrier aggregation is supported, and, unlike in LTE, multiple component carriers (CCs) or serving cells may be assigned to the uplink, downlink, or both. Such carriers may be asymmetric. For example, different number of CCs may be assigned to the uplink than the number of CCs assigned to the downlink.
In LTE Release 8, channel state information (CSI) is designed to fit the operation of simple single component carrier. A CSI report may include CQI. With carrier aggregation, however, a wireless transmit receive unit (WTRU) may send a periodic channel quality report for multiple, such as for up to the maximum number of downlink CCs that may be configured for the WTRU, onto one WTRU-specific UL CC. Thus in LTE-A, the amount of periodic feedbacks to be transmitted by a UE may increase considerably compared to that of LTE Rel-8 on a given UL CC. Issues pertaining to periodic CSI reporting in carrier aggregation may easily be extended to aperiodic CSI reporting. For example, a UE may be expected to send an aperiodic channel quality report for multiple DL CCs onto one WTRU specific UL CC. However, current mechanisms may not accommodate the increased demand in periodic and aperiodic CSI reporting. For example, current mechanisms may not support transmitting CSI for multiple carriers over Physical Uplink Control Channel (PUCCH), transmit CSI over DFT-S-OFDM-based PUCCH, or multiplex certain CSI over PUCCH.